A typical wireless communication network (e.g., Frequency Division Multiple Access (FDMA), Time Division Multiple Access (TDMA) and Code Division Multiple Access (CDMA)) includes one or more base stations that provide a coverage area and one or more mobile (e.g., wireless) terminals that can transmit and receive data within the coverage area. A typical base station can simultaneously transmit multiple data streams for broadcast, multicast, and/or unicast services, wherein a data stream is a stream of data that can be of independent reception interest to a mobile station. A mobile station within the coverage area of that base station can be interested in receiving one, more than one or all the data streams carried by the composite stream. Likewise, a mobile station can transmit data to the base station or another mobile station. Such communication between base station and mobile station or between mobile stations can be degraded due to channel variations and/or interference power variations. Service quality may also be impacted by congestion in at least some types of wireless networks.
Cellular wireless communication systems are designed to serve many MS's distributed in a large geographic area by dividing the area into cells. At the center of each cell, a base station is located to serve mobile stations operating in the area of the cell. Each cell can be further divided into sectors by using multiple sectorized antennas. Typically three sectors per cell are used. The term sector is used, however, even when there is only one sector per cell. In each cell, a base station serves one or more sectors and communicates with multiple mobile stations in its cell. The communication between the base station and the mobile station uses analog modulation (such as analog voice) or digital modulation (such as digital voice or digital packet data) to transmit and receive such data (analog or digital).
Among cellular networks, FDMA and TDMA networks have fixed numbers of traffic channels determined by time slots in the TDMA and the number of frequency channels in the FDMA. In the FDMA and TDMA systems, traffic channels are allocated to users as long as there are available channels among the fixed number of channels. On the other hand, in the communication systems based on CDMA-technology and its derivatives, the capacity of currently-known wireless systems—the number of mobile station users that can be supported—is limited by the number of available Walsh codes set by wireless standards. Although it is possible to increase the capacity of CDMA signal carriers, the number of available Walsh codes is still fixed. Moreover, since the Quality of Service (QoS) degrades as the number of mobile station users increases, the number of traffic channels set by the available Walsh codes cannot be fully taken advantage of to guarantee some level of QoS of voice calls to the mobile station users.
Furthermore, the capacity of the CDMA system is also limited by multi-user interference occurring between the transceivers using the same carrier frequency, and by fading of the communication channels due to multi-path propagation of a radio signal. Since the CDMA systems employ the cellular network in which a number of radio cells, each of which is made of several sectors, are used to provide radio coverage over a wide area than the area of one cell, the system is subject to interferences not only from MS's within a sector but also from MS's within neighboring cells or sectors. As the number of mobile station users in a sector or a cell increases, the overall level of interferences to the CDMA system increases. Thus, in practical situations, the capacity of the CDMA system set by the available Walsh codes is inapplicable. Instead, the capacity of the CDMA system depends largely on the interference conditions determined by network environment such as sector layout, inter-site distance and physical landscape. It is desirable to know the capacity of the CDMA system in a cell or a sector to manage wireless communication resources while ensuring QoS of the wireless communications provided to the users of the mobile stations.
The communication environment, which affects the call capacity of the CDMA system, such as number of mobile stations in a sector and geographical environment, varies depending upon the sector and time. Thus, the call capacity also changes according to time and the sector. It is desirable to measure the call capacity in a real time.
Thus, a need exists for measuring the capacity of the CDMA system in an individual cell automatically and dynamically, since the interference levels vary dynamically in response to change of the network environment.